1. Field of the Invention
This invention relates to windshield wipers, particularly heated windshield wipers.
2. The Prior Art
Various cold weather windshield wipers have been devised to prevent or minimize snow and ice buildup thereon, which can impair the effectiveness of the wiper blades in clearing the windshield of precipitation, resulting in reduced or blocked visibility therethrough. In such prior art heated wipers, electrical heating elements have been imbeded either near or in the wiper blades, which proximity frequently has caused damage to such blades when sufficient heat was applied to the heating elements to melt snow and ice thereon e.g. at about 180.degree. F. or more. To prevent such overheating, thermostats have been added to the heating circuits of some prior art heated wipers with the intention of interrupting the flow of current from auto battery to blade heating elements before such blade damaging temperatures would be reached. However, these DC operated thermostats have frequently fused and blade overheating and damage occurred
Attempts were then made in the prior art to mount the wiper blade in a holder e.g. of plastic and then mount the heating element in such holder to apply heat to the wiper blade indirectly to prolong the life thereof. One example of this approach is U.S. Pat. No. 4,194,261 to Parkinson (1980). As shown in FIGS. 1 to 3 of this reference, Parkinson provides a rather thick holder or backing member that has a longitudinal groove on its underside for holding the wiper blade thereto and a longitudinal groove on its upper side for holding a heating element therein, which groove has a pair of upwardly converging side walls 38 and 40, which together with wire insulation 98, enclose the heating element 88 therein. Fins 46 and 48 of the holder are believed to mount in a wiper housing, which however is not shown. However, such holder in providing a superstructure (the converging side walls 38 and 40) to enclose the above element has three problems; (a) it is too thick and stiff to follow any significant windshield curvature and thus cannot sweep same clear of water, snow, ice and the like. Also, as the heating element in this reference is totally enclosed in the holder, (b) excessive heat build-up therein can cause softening of the plastic and weakening and distortion thereof. Further, (c) insufficient heat from the so-enclosed heating element can be transmitted to the wiper housing for prevention of snow and ice build-up thereon. Accordingly, there is a need and market for a heated wiper blade that is durable and that overcomes the above prior art shortcomings.
There has now been developed a heated wiper blade that has a holder that protects the wiper blade from direct application of heat thereto, yet is sufficiently flexible to follow curved windshield contours without early fatigue problems and also provides sufficient heat to the wiper housing to minimize or prevent snow and ice buildup thereon.